1. Field of the Invention
The present invention relates to a wafer processing method for dividing, along plural division lines, a wafer in which devices are formed in plural areas partitioned by the division lines formed in a lattice manner in a functional layer stacked on a surface of a substrate.
2. Description of the Related Art
Recently, a semiconductor wafer has been put into practical use with a form in which semiconductor devices are formed by a functional layer including a low dielectric constant insulator coat (Low-k film) that is formed over a surface of a substrate of silicon or the like and is formed of a film based on an inorganic substance such as SiOF or BSG (SiOB) or a film based on an organic substance as a polymer film of a polyimide-based material, a parylene-based material, or the like in order to improve the processing ability of semiconductor chips such as ICs and LSIs. The Low-k film is difficult to cut by a cutting blade. Specifically, the Low-k film is very fragile like mica and therefore involves the following problem. When cutting is performed by a cutting blade along the division line, the Low-k film peels off and this peeling reaches circuitry, which gives fatal damage to the devices.
To solve the above-described problem, the following wafer dividing method is disclosed in Japanese Patent Laid-open No. 2005-64231. Specifically, irradiation with a laser beam is performed along division lines formed on a semiconductor wafer to form laser-processed grooves along the division lines and split a functional layer. Then, a cutting blade is positioned to the laser-processed groove and the cutting blade and the semiconductor wafer are moved relative to each other to cut the semiconductor wafer along the division lines.